Method for manufacturing electrolyte solution material

ABSTRACT

An electrolytic solution comprising N-(fluorosulfonyl)-N-(fluoroalkylsulfonyl)imide or di(fluorosulfonyl)imide, from which a residual solvent that affects the properties of the electrolyte solution material is reduced, is provided. A method for producing an electrolyte solution material containing fluorosulfonyl imide salt represented by the following general formula (1) and an electrolyte solution preparation solvent comprises decompressing and/or heating a solution containing the fluorosulfonyl imide salt and the electrolyte solution preparation solvent to volatilize a production solvent for the fluorosulfonyl imide salt.In general formula (1), R1 represents a fluorine atom or a fluorinated alkyl group having 1 to 6 carbon atoms, R2 represents an alkali metal ion.

TECHNICAL FIELD

The present invention relates to a fluorosulfonyl imide, and moreparticularly to an electrolyte solution material containingN-(fluorosulfonyl)-N-(fluoroalkylsulfonyl)imide ordi(fluorosulfonyl)imide and a method for producing the same.

BACKGROUND ART

A fluorosulfonyl imide such asN-(fluorosulfonyl)-N-(fluoroalkylsulfonyl)imide,di(fluorosulfonyl)imide, and derivatives thereof are useful asintermediates for compounds having a N(SO₂F) group or an N(SO₂F)₂ group,and are also useful compounds in various applications, for example,electrolytes, additives for electrolyte solutions of fuel cells,selective electrophilic fluorinating agents, photo-acid generators,thermal acid generators, and near infrared light-absorbing dyes. Inaddition, however, a fluorosulfonylimide is such a compound that it isquite difficult to remove impurities therefrom due to outstandingpolarity thereof.

Patent Document 1 discloses a method for producing a powder by removinga reaction solvent from an alkali metal salt of a fluorosulfonylimide.In this document, the problem that the alkali metal salt of thefluorosulfonylimide has high affinity for the reaction solvent andtherefore it is difficult to remove the solvent is disclosed, and asolvent distillation method for solving the problem is also disclosed.

PRIOR ART DOCUMENT Patent Document

-   Patent Document 1: WO 2011/149095

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

However, in the production method disclosed in Patent Document 1, about1000 ppm of a residual solvent (particularly a solvent used in theproduction of a fluorosulfonylimide) still remains in the alkali metalsalt of the fluorosulfonylimide. Furthermore, once thefluorosulfonylimide salt is formed into a powder, the residual solvent(the above-mentioned production solvent) is incorporated into the powderand therefore it is difficult to remove the residual solvent merely bydrying. For example, in the case where the fluorosulfonylimide salt isintended to be used as an electrolytic substance for a lithium battery,the residual solvent may cause the swelling of a battery. Particularly ahalogen-based solvent can cause the corrosion of an aluminum currentcollector in a lithium battery upon the decomposition of thehalogen-based solvent, and therefore it is required to reduce the amountof the residual solvent particularly in an electrolyte solution to beused in an automotive battery that is intended to be used for a longperiod.

Thus, the present invention is made with focusing attention on theabove-mentioned situations. The object of the present invention is toprovide: an electrolyte solution material from which a residual solventthat may affect the properties of the electrolyte solution material isreduced; and a method for producing the electrolyte solution material.

Means for Solving the Problems

The production method according to the present invention by which theabove-mentioned problem can be solved is a method for producing anelectrolyte solution material containing a fluorosulfonylimide saltrepresented by general formula (1) and a solvent for an electrolytesolution, and is characterized in decompressing and/or heating asolution containing the fluorosulfonylimide salt and the electrolytesolution solvent to volatilize a fluorosulfonylimide salt productionsolvent.

In general formula (1), R₁ represents a fluorine atom or a fluorinatedalkyl group having 1 to 6 carbon atoms, and R₂ represents an alkalimetal ion. The electrolyte solution solvent is preferably a cycliccarbonate-based solvent or a cyclic ester-based solvent.

The present invention also includes, within the scope thereof, a methodfor producing a non-aqueous electrolyte solution, comprising mixing theelectrolyte solution material produced by the above-mentioned methodwith a non-aqueous electrolyte solution preparation solvent.

In addition, the present invention also includes, within the scopethereof, an electrolyte solution material comprising thefluorosulfonylimide salt represented by general formula (1) and anelectrolyte solution solvent, wherein a concentration of thefluorosulfonylimide salt contained in the electrolyte solution materialis 30% by mass or more and a residual amount of a fluorosulfonylimidesalt production solvent contained in the electrolyte solution materialis 3000 ppm or less.

In this case, it is preferred that a cyclic carbonate-based solvent or acyclic ester-based solvent is contained in an amount of 90% by mass ormore in the electrolyte solution solvent.

In addition, the present invention also includes, within the scopethereof: a non-aqueous electrolyte solution produced from theelectrolyte solution material; and an electrical storage device providedwith the non-aqueous electrolyte solution.

In addition, the present invention also includes, within the scopethereof: a method for storing an electrolyte solution material,comprising storing an electrolyte solution material containing thefluorosulfonylimide salt represented by general formula (1) and anelectrolyte solution solvent, wherein a concentration of thefluorosulfonylimide salt is 30% by mass or more; and a method fortransporting an electrolyte solution material, comprising transportingan electrolyte solution material containing the fluorosulfonylimide saltrepresented by general formula (1) and an electrolyte solution solvent,wherein the concentration of the fluorosulfonylimide salt is 30% by massor more.

In the present invention, an electrolyte solution solvent is added to afluorosulfonylimide salt which is formed into a powder and into whichthe residual solvent is incorporated to dissolve the fluorosulfonylimidesalt in the electrolyte solution solvent, thereby producing a solution.In this case, the residual solvent becomes more volatilizable, and theelectrolyte solution solvent has higher affinity for thefluorosulfonylimide salt than the residual solvent. Therefore, theresidual solvent can be removed with higher efficiency by decompressionand/or heating. Furthermore, the resultant solution can be used as anelectrolyte solution material without any modification. The presentinvention enables the removal of the residual solvent from the powder,and also enables the removal of the residual solvent from a solutionhaving the fluorosulfonylimide salt dissolved in the residual solvent byadding the electrolyte solution solvent and then decompressing and/orheating the resultant solution.

Effect of the Invention

According to the present invention, it is possible to produce anelectrolyte solution material containingN-(fluorosulfonyl)-N-(fluoroalkylsulfonyl)imide ordi(fluorosulfonyl)imide, from which a residual solvent that affects theproperties of the electrolyte solution material is reduced. Because theelectrolyte solution material has a liquid form, the need for a facilityfor handing a highly hygroscopic fluorosulfonylimide salt powder can beeliminated and therefore the cost of the production of the product canbe reduced. Furthermore, a non-aqueous electrolyte solution can beproduced from the electrolyte solution material according to the presentinvention without any modification or by merely diluting the electrolytesolution material according to the present invention, and therefore theworkability can be improved and the non-aqueous electrolyte solution canbe produced in a simple manner at low cost. In addition, when theelectrolyte solution material, which has a liquid form, is preparedpreviously, an effect of reducing the amount of heat (dissolution heat)generated upon mixing the fluorosulfonylimide salt powder with anelectrolyte solution solvent can also be achieved. The electrolytesolution material according to the present invention also has theadvantage that the electrolyte solution material generates HF in areduced amount during the storage of the electrolyte solution materialin the form of a solution.

When an electrolyte solution material containing the fluorosulfonylimidesalt represented by general formula (1) (also referred to as“fluorosulfonylimide salt (1)”, hereinafter) and a cycliccarbonate-based solvent or a cyclic ester-based solvent as the maincomponents is used, the increase in temperature to a temperature atwhich a non-aqueous electrolyte solution can be decomposed can beprevented, and the need for adjusting the rate of addition of thefluorosulfonylimide salt (1) in the preparation of the non-aqueouselectrolyte solution can be eliminated, resulting in the improvement inproductivity. Thus, according to the method of the present invention, afluorosulfonylimide salt-containing non-aqueous electrolyte solutionhaving better quality can be produced within a shorter time comparedwith the conventional production methods.

MODE FOR CARRYING OUT THE INVENTION

The present inventors have made studies for the purpose of providing amethod for producing a non-aqueous electrolyte solution containing afluorosulfonylimide salt (1) and having better quality compared with theconventional ones with high efficiency. As a result, it is found that,when an electrolyte solution material which contains afluorosulfonylimide salt (1) and a cyclic carbonate-based solvent or acyclic ester-based solvent as the main components and which is preparedpreviously is used as a starting material for a non-aqueous electrolytesolution, it becomes possible to produce the non-aqueous electrolytesolution within a shorter time compared with the conventional methodswhile preventing the heat-induced deterioration of the non-aqueouselectrolyte solution and while keeping the quality of the non-aqueouselectrolyte solution at a good level even when an electrolyte solutionpreparation solvent or another electrolyte salt is added to theelectrolyte solution material in the subsequent non-aqueous electrolytesolution production process. This finding leads to the accomplishment ofthe present invention.

First, the details of the accomplishment of the present invention willbe described. Heretofore, in the production of a non-aqueous electrolytesolution, a solvent solution comprising a mixture of all of electrolytesolution preparation solvents to be used, e.g., ethylene carbonate,methyl ethyl carbonate, diethyl carbonate, is prepared previously, andthen an electrolyte salt, e.g., a fluorosulfonylimide salt (1), is addedto the solvent solution. In the preparation of the solvent solution,ethylene carbonate has a solid form at ambient temperature and thereforeis usually heated to a temperature higher than the melting point ofethylene carbonate (generally a temperature higher than 50° C.) and isthen added to another electrolyte solution preparation solvent. As aresult, the temperature of the solvent solution at which thefluorosulfonylimide salt (1) is to be added is increased, and thereforethe temperature of the solution is increased to a temperature not lowerthan 60° C. by an exothermal reaction occurring upon the addition of thefluorosulfonylimide salt (1), resulting in the deterioration in thenon-aqueous electrolyte solution. For the purpose of solving thisproblem, it has been needed to control the rate of addition of thefluorosulfonylimide salt (1) so as to control the increase intemperature of the solution. In this case, however, it takes long timeto prepare the non-aqueous electrolyte solution and productivity isunsatisfactory, resulting in the increase in cost, as mentioned above.

Thus, the present inventors have made studies on the non-aqueouselectrolyte solution production processes. As a result, it is foundthat: when an electrolyte solution material that contains afluorosulfonylimide salt (1) and a cyclic carbonate-based solvent or acyclic ester-based solvent as the main components and is preparedpreviously is used, a heat treatment of the cyclic carbonate-basedsolvent or the cyclic ester-based solvent each having a solid form,which has been needed in the conventional non-aqueous electrolytesolution production processes, can be eliminated; and when anelectrolyte solution material having a temperature of about roomtemperature is used as a starting material and a desired non-aqueouselectrolyte solution preparation solvent and a desired electrolyte saltare added to the electrolyte solution material, even if an exothermalreaction occurs as the result of the above-mentioned addition, thetemperature of the solution never increases to a temperature at whichthe electrolyte can be decomposed, and therefore the need forcontrolling the electrolyte salt addition rate for temperaturecontrolling purposes, which has been needed in the conventional methods,can also be eliminated, resulting in the achievement of the preparationof a non-aqueous electrolyte solution within a short time. This findingleads to the accomplishment of the present invention.

The term “fluorosulfonyl imide” in the present invention includes, inaddition to di(fluorosulfonyl)imide having two fluorosulfonyl groups,N-(fluorosulfonyl)-N-(fluoroalkylsulfonyl)imide having a fluorosulfonylgroup and a fluorinated alkyl group. The term “chlorosulfonylimide”,which is a starting material, is the same.

The production method according to the present invention is a method forproducing an electrolyte solution material containing thefluorosulfonylimide salt represented by general formula (1) and asolvent, and is characterized in decompressing and/or heating a solutioncontaining the fluorosulfonylimide salt and the electrolyte solvent tovolatilize the fluorosulfonylimide salt production solvent (wherein thestep is also referred to as a “volatilization step, hereinafter). Theterm “fluorosulfonylimide salt production solvent” as used herein refersto a solvent which is used in the production of the fluorosulfonylimidesalt and is contained in a fluorosulfonylimide salt produced by theconventional production method, and has the same meaning as the term“residual solvent”.

The compound represented by general formula (1) includes a compoundwherein R₁ represents a fluorine atom or a fluorinated alkyl grouphaving 1 to 6 carbon atoms. The number of carbon atoms in thefluorinated alkyl group is preferably 1 to 6, more preferably 1 to 4.Specific examples of the fluorinated alkyl group having 1 to 6 carbonatoms include a fluoromethyl group, a difluoromethyl group, atrifluoromethyl group, a fluoroethyl group, a difluoroethyl group, a2,2,2-trifluoroethyl group, a pentafluoroethyl group, a3,3,3-trifluoropropyl group, a perfluoro-n-propyl group, a fluoropropylgroup, a perfluoroisopropyl group, a fluorobutyl group, a3,3,4,4,4-pentafluorobutyl group, a perfluoro-n-butyl group, aperfluoroisobutyl group, a perfluoro-t-butyl group, aperfluoro-sec-butyl group, a fluoropentyl group, a perfluoropentylgroup, a perfluoroisopentyl group, a perfluoro-t-pentyl group, afluorohexyl group, a perfluoro-n-hexyl group and a perfluoroisohexylgroup. Among these groups, R₁ is preferably a fluorine atom, atrifluoromethyl group, a pentafluoroethyl group or a perfluoro-n-propylgroup, more preferably a fluorine atom, a trifluoromethyl group or apentafluoroethyl group.

R₂ is a cation constituting the compound (1), and represents an alkalimetal ion. Specific examples of the alkali metal element includelithium, sodium, potassium, rubidium and cesium. Among them, the alkalimetal element is preferably lithium, sodium or potassium, morepreferably lithium.

Examples of the compound represented by general formula (1) includelithium di(fluorosulfonyl)imide, sodium di(fluorosulfonyl)imide, lithium(fluorosulfonyl)(trifluoromethylsulfonyl)imide, sodium(fluorosulfonyl)(trifluoromethylsulfonyl)imide, lithium(fluorosulfonyl)(pentafluoroethylsulfonyl)imide and the like. Thecompound represented by general formula (1) is more preferably lithiumdi(fluorosulfonyl)imide and lithium(fluorosulfonyl)(trifluoromethylsulfonyl)imide.

In the present invention, the method for synthesizing thefluorosulfonylimide salt represented by compound (1) is not particularlylimited, and any one of the conventional known methods can be employed.For example, methods disclosed in WO2011/149095, Japanese UnexaminedPatent Application Publication (JP-A) No. 2010-189372, JapaneseUnexamined Patent Application Publication (Translation of PCTApplication) No. Hei 8-511274, WO2012/108284, WO2012/117961,WO2012/118063, JP-A No. 2010-280586, JP-A No. 2010-254543, JP-A No.2007-182410, WO2010/010613 and the like are exemplified.

The method for producing an electrolyte solution material containing thefluorosulfonylimide salt represented by general formula (1) and asolvent for an electrolyte solution according to the present inventionis characterized by comprising a step of decompressing and/or heating asolution, which is prepared by mixing the fluorosulfonylimide salt withthe electrolyte solution solvent, to volatilize a fluorosulfonylimidesalt production solvent. As mentioned above, even when thefluorosulfonylimide salt is isolated in the form of a powder (a solidmaterial), the fluorosulfonylimide salt still contains a solvent usedbefore the isolation (wherein the solvent is also referred to as a“residual solvent” or a “production solvent”, hereinafter). Theconcentration of the production solvent in the powder can be reduced bydecompressing and/or heating the solution having the fluorosulfonylimidesalt dissolved in the electrolyte solution solvent to volatilize thefluorosulfonylimide salt production solvent. In the method for producingthe electrolyte solution material according to the present invention, itis also possible to add the electrolyte solution solvent to a solutionproduced by the production or purification of the fluorosulfonylimidesalt (i.e., a solution containing the fluorosulfonylimide salt and thesolvent) and then decompress and/or heat the resultant solution tovolatilize the production solvent. It is also possible to produce thefluorosulfonylimide salt in this manner and subsequently produce theelectrolyte solution material containing the fluorosulfonylimide saltand the electrolyte solution solvent.

The electrolyte solution solvent has higher affinity for the compound(1) and a higher boiling point compared with those of the residualsolvent, and therefore the residual solvent can be volatilized andremoved with higher efficiency by decompression and/or heating.

The term “residual solvent” as used herein refers to a solvent used inthe reaction for producing the compound (1) or a solvent used in a stepof purifying the compound (1). According to the classification of theresidual solvent and the below-mentioned electrolyte solvent on thebasis of the affinity thereof, specific examples of a solvent having amoderate level of affinity for the compound (1) include: water; analcohol-based solvent, such as methanol, ethanol, propanol and butanol;a carboxylic acid-based solvent, such as formic acid and acetic acid; aketone, such as acetone, methyl ethyl ketone, methyl isobutyl ketone anddiisobutyl ketone; a nitrile-based solvent, such as isobutyronitrile,acetonitrile, valeronitrile and benzonitrile; an ester-based solvent,such as ethyl acetate, isopropyl acetate and butyl acetate; an aliphaticether-based solvent, such as diethyl ether, diisopropyl ether, t-butylmethyl ether and cyclopentyl methyl ether; a halogen-based solvent, suchas HF; a nitro-group-containing solvent, such as nitromethane andnitrobenzene; a nitrogenated organic solvent, such as ethylformamide andN-methylpyrrolidone; dimethyl sulfoxide; and a glyme-based solvent.Among these solvents, acetonitrile, valeronitrile, ethyl acetate,isopropyl acetate, butyl acetate and cyclopentyl methyl ether arepreferred. Specific examples of a solvent having low affinity for thecompound (1) include: an aromatic hydrocarbon-based solvent, such astoluene, o-xylene, m-xylene, p-xylene, benzene, ethylbenzene,isopropylbenzene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene,1,3,5-trimethylbenzene, tetralin, cymene, methylethylbenzene,2-ethyltoluene, chlorobenzene and dichlorobenzene; a linear aliphatichydrocarbon-based solvent, such as pentane, hexane, heptane, octane,decane, dodecane, undecane, tridecane, decalin,2,2,4,6,6-pentamethylheptane, isoparaffin (e.g., “MARUKASOL R” (amixture of 2,2,4,6,6-pentamethylheptane and2,2,4,4,6-pentamethylheptane, manufactured by Maruzen Petrochemical Co.,Ltd.), “Isopar (registered trademark) G” (a C9-C11-mixed isoparaffin,manufactured by Exxon Mobil Corporation), “Isopar (registered trademark)E” (a C8-C10-mixed isoparaffin, manufactured by Exxon MobilCorporation)), dichloromethane, chloroform and 1,2-dichloroethane; acyclic aliphatic hydrocarbon-based solvent, such as cyclohexane,methylcyclohexane, 1,2-dimethylcyclohexane, 1,3-dimethylcyclohexane,1,4-dimethylcyclohexane, ethylcyclohexane, 1,2,4-trimethylcyclohexane,1,3,5-trimethylcyclohexane, propylcyclohexane, butylcyclohexane and“SWACLEAN 150” (a C9-alkylcyclohexane mixture, manufactured by MaruzenPetrochemical Co., Ltd.); and an aromatic ether-based solvent, such asanisole, 2-methylanisole, 3-methylanisole and 4-methylanisole. Thesesolvents may be used singly, or two or more of them may be used in theform of a mixture. Among these solvents, toluene, o-xylene, m-xylene,p-xylene, ethylbenzene, isopropylbenzene, 1,2,4-trimethylbenzene,hexane, heptane, chlorobenzene, dichlorobenzene, dichloromethane and1,2-dichloroethane are preferred.

The electrolyte solution solvent to be used in the present invention hashigher affinity for the compound (1) compared with the residual solvent,and can be used suitable in the volatilization step. The electrolytesolvent to be used is a solvent that can be used as an electrolytesolution material without any modification. When the electrolyte solventof this type is used, the residual solvent can be removed with highefficiency. The electrolyte solution material according to the presentinvention may be mixed with a solvent, an additive, an electrolyte andthe like which are needed for the electrolyte solution material. Theresultant mixture can be used without any modification as an electrolytesolution for a lithium secondary battery. The electrolyte solvent to beused can be selected appropriately depending on the affinity of theelectrolyte solvent for the compound (1), the affinity of the residualsolvent for the general formula (1), the boiling points of the solventsand the like. Specific examples of the solvent having high affinity forthe compound (1) include: a carbonate-based solvent, such as ethylenecarbonate, propylene carbonate, butylene carbonate, dimethyl carbonate,ethylmethyl carbonate and diethyl carbonate; a linear ether-basedsolvent, such as dimethoxymethane and 1,2-dimethoxyethane; a cyclicether-based solvent, such as tetrahydrofuran, 2-methyltetrahydrofuran,1,3-dioxane and 4-methyl-1,3-dioxolane; a cyclic ester-based solvent,such as γ-butyrolactone and γ-valerolactone; a sulfolane-based solvent,such as sulfolane and 3-methylsulfolane; and N,N-dimethylformamide,dimethyl sulfoxide and N-methyloxazolidinone. These solvents may be usedsingly, or two or more of them may be used in the form of a mixture.Among these exemplified solvents, a carbonate-based solvent such asethylene carbonate, propylene carbonate, butylene carbonate, dimethylcarbonate, ethylmethyl carbonate and diethyl carbonate (particularly acyclic carbonate, such as ethylene carbonate, propylene carbonate andbutylene carbonate) and a cyclic ester-based solvent such asγ-butyrolactone and γ-valerolactone are preferred.

In the method for producing the electrolyte solution material accordingto the present invention, the solution to be used in the volatilizationstep can be prepared by mixing the electrolyte solution solvent with apowder of the fluorosulfonylimide salt represented by general formula(1). Alternatively, the volatilization step may be carried out by mixingthe electrolyte solution solvent with a solution produced by theproduction and purification of the fluorosulfonylimide salt representedby general formula (1) in a solvent.

In the method for producing the electrolyte solution material accordingto the present invention, the lower limit of the amount of the residualsolvent to be contained before the volatilization step is notparticularly limited. For example, the amount is preferably 1000 g orless, more preferably 100 g or less, still more preferably 10 g or less,most preferably 1 g or less, relative to 100 g of thefluorosulfonylimide salt represented by general formula (1). When theamount of the residual solvent is large, it is undesirable because theamount of the electrolyte solution solvent to be used is also increasedand the time required for the volatilization is prolonged. In the casewhere a solution produced by the production and purification of thefluorosulfonylimide salt represented by general formula (1) in asolution is used in the volatilization step, it is preferred to distilaway the solvent prior to the volatilization step (i.e., prior to theaddition of the electrolyte solution solvent) to reduce the amount ofthe contained residual solvent so as to adjust the amount of theresidual solvent to a value falling within the above-mentioned range.

In the method for producing the electrolyte solution material accordingto the present invention, the lower limit of the amount of theelectrolyte solution solvent to be used is not particularly limited, andcan be adjusted appropriately depending on the amount of the residualsolvent and the like. For example, the amount is preferably not morethan 10000 g, more preferably 1000 g or less, still more preferably 500g or less, still more preferably 200 g or less, still more preferably100 g or less, most preferably 50 g or less, relative to 100 g of thefluorosulfonylimide salt represented by general formula (1).

In the method for producing the electrolyte solution material accordingto the present invention, the amount of the electrolyte solvent to beused is, for example, preferably 1 to 1000 parts by mass, morepreferably 5 to 500 parts by mass, still more preferably 10 to 300 partsby mass, particularly preferably 30 to 200 parts by mass, moreparticularly preferably 50 to 100 parts by mass, relative to 100 partsby mass of the fluorosulfonylimide salt represented by general formula(1).

The volatilization step may be any one as long as a step ofdecompressing and/or heating the fluorosulfonylimide salt represented bygeneral formula (1) and the electrolyte solution solvent is involvedtherein, and can be performed under ambient pressure or a reducedpressure. From the viewpoint of avoiding the decomposition of thefluorosulfonylimide salt by heat, it is desirable to perform thevolatilization step under a reduced pressure. The degree of reduction inpressure is not particularly limited, and can be adjusted appropriatelydepending on the types of the residual solvent and the types of theelectrolyte solution solvent. For example, the degree of reduction inpressure is preferably 200 kPa or less, more preferably 40 kPa or less,still more preferably 15 kPa or less, particularly preferably 5 kPa orless.

The volatilization temperature is not particularly limited, and can beadjusted appropriately depending on the degree of reduction in pressure,the types of the residual solvent and the types of the electrolytesolution solvent. From the viewpoint of avoiding the decomposition ofthe fluorosulfonylimide salt by heat, it is desirable to perform thevolatilization step at a relatively low temperature. For example, thevolatilization temperature is preferably 10 to 110° C., more preferably15 to 80° C., still more preferably 20 to 60° C., particularlypreferably 30 to 50° C.

The time for the volatilization is not particularly limited, and can beadjusted appropriately depending on the degree of reduction in pressure,the heating temperature, the amount of the residual solvent and thelike. For example, the time for the volatilization is preferably 0.1 to24 hours, more preferably 0.5 to 12 hours, still more preferably 1 to 8hours, particularly preferably 2 to 5 hours.

The device to be used for the volatilization step and capable ofachieving the decompression and/or heating may be selected appropriatelydepending on the volume of the solution, the degree of reduction inpressure, the heating temperature and the like. For example, a tank-typereactor and a tank-type reactor which is capable of reducing an internalpressure can be mentioned.

The concentration of the fluorosulfonylimide salt represented by generalformula (1) to be contained in the electrolyte solution material is notlimited particularly, and can be adjusted appropriately depending on thetypes of the electrolyte solvent. For example, the concentration ispreferably 15 to 95% by mass, more preferably 20 to 90% by mass, stillmore preferably 30 to 90% by mass. In the production of a non-aqueouselectrolyte solution by adding the organic solvent to the electrolytesolution material, from the viewpoint of appropriately setting theconcentration of the electrolyte salt in the non-aqueous electrolytesolution, the concentration of the fluorosulfonylimide salt representedby general formula (1) to be contained in the electrolyte solutionmaterial is preferably 30% by mass or more, more preferably 40% by massor more, still more preferably 50% by mass or more. When the electrolytesolution material according to the present invention contains thefluorosulfonylimide salt represented by general formula (1) at aconcentration of not less than 30% by mass, good stability can beachieved and the generation of HF (hydrofluoric acid), which can causethe corrosion of a container for storage or transport use, can beprevented, and therefore this concentration is also suitable for thestorage and transport of the fluorosulfonylimide salt represented bygeneral formula (1).

As the electrolyte solvent to be contained in the electrolyte solutionmaterial according to the present invention, those electrolyte solventswhich are mentioned specifically above can be used. It is preferred tocontain a cyclic carbonate, such as ethylene carbonate, propylenecarbonate and butylene carbonate, or a cyclic ester-based solvent, suchas γ-butyrolactone and γ-valerolactone. Among these solvents, ethylenecarbonate or γ-butyrolactone is preferably contained, and ethylenecarbonate is particularly preferred. It is preferred to contain thecyclic carbonate or the cyclic ester-based solvent in an amount of 90%by mass or more, more preferably 95% by mass or more, still morepreferably 98% by mass or more, relative to the total amount of theelectrolyte solvents.

The amount of the residual solvent in the electrolyte solution materialis not particularly limited, and can be appropriately adjusted dependingon the concentration of the electrolyte solution material and the typesof the residual solvent. For example, the amount is preferably not morethan 3000 ppm, more preferably 2000 ppm or less, still more preferably1000 ppm or less, particularly preferably 500 ppm or less, mostpreferably 200 ppm or less. When the remaining amount of thefluorosulfonylimide salt production solvent in the electrolyte solutionfalls within the above-mentioned range, the amount of the solvent in theresultant non-aqueous electrolyte solution can be reduced. Therefore, ina battery produced using the non-aqueous electrolyte solution, theoccurrence of any side reaction upon the actuation of the battery can beprevented, thereby the swelling of the battery is suppressed.

After the completion of the volatilization step, the product may besubjected to filtration, a column chromatography, purification, anactivated carbon treatment, a molecular sieve treatment or the like, ifnecessary.

The electrolyte solution material produced by the production methodaccording to the present invention can be used suitably as a materialfor an ionic conductor that constitutes a primary battery, a batteryhaving a charge/discharge mechanism, such as a lithium ion secondarybattery and a fuel cell or an electrical storage device (anelectrochemical device) such as an electrolytic capacitor, an electricdouble-layer capacitor and a solar cell, and an electrochromic displayelement.

The present invention also includes, within the scope thereof; anon-aqueous electrolyte solution produced using the electrolyte solutionmaterial; and a method for producing a non-aqueous electrolyte solutionusing the electrolyte solution material. A non-aqueous electrolytesolution can be produced by mixing a non-aqueous electrolyte solutionpreparation solvent with the electrolyte solution material, ifnecessary. In the non-aqueous electrolyte solution, various types ofelectrolytes, additives and the like may be added for the purpose ofimproving battery properties. It is also possible to add a solventsuitable for the dissolution of an electrolyte or the like to theelectrolyte solution material. In the preset invention, the non-aqueouselectrolyte can be prepared by adding a desired solvent to theelectrolyte solution material.

The electrolyte solution preparation solvent to be used is notparticularly limited, as long as the solvent is compatible with theelectrolyte solvent and can dissolve and disperse a desired electrolytesalt therein. In the present invention, any one of the conventionalknown solvents that can be used in batteries, such as a non-aqueoussolvent and a medium (e.g., a polymer, a polymer gel) that can be usedin place of the solvent, can be used. In the electrolyte solutionmaterial, the electrolyte solvent is contained. If required, theelectrolyte solution material may additionally be added a solvent thatis of the same type as the electrolyte solvent, and any one of theabove-mentioned electrolyte solvents may be used as the solvent. Theelectrolyte solution preparation solvent may be in a liquid form or asolid form, and is preferably in a liquid form from the viewpoint of theachievement of highly efficient mixing. The temperature of theelectrolyte solution preparation solvent is not particularly limited.The temperature may be room temperature, and may be adjustedappropriately as required.

Among the electrolyte solution preparation solvents, a carbonate ester(a carbonate-based solvent) such as a linear carbonate ester and acyclic carbonate ester, a lactone and an ether are preferred; dimethylcarbonate, ethylmethyl carbonate, diethyl carbonate, ethylene carbonate,propylene carbonate, γ-butyrolactone, γ-valerolactone and the like aremore preferred; and a carbonate-based solvent such as dimethylcarbonate, ethylmethyl carbonate, diethyl carbonate, ethylene carbonateand propylene carbonate is still more preferred. These solvents may beused singly, or two or more of them may be used in combination.

In the present invention, if necessary, an electrolyte salt that isdifferent from the fluorosulfonylimide salt (1) (also referred to as“another electrolyte salt”, hereinafter) may be mixed with theelectrolyte solution material. The above-mentioned another electrolytesalt may be added to the electrolyte solution material to which theelectrolyte solution preparation solvent is not added yet. From theviewpoint of the dissolution efficiency of the above-mentioned anotherelectrolyte salt, it is desirable to add the above-mentioned anotherelectrolyte salt after the addition of the electrolyte solutionpreparation solvent to the electrolyte solution material. For example,in the case where the above-mentioned another electrolyte salt to beadded is poorly soluble in ethylene carbonate, like LiPF₆, it isdesirable to add the electrolyte salt after the addition of a solventsuitable for the dissolution of the electrolyte salt, as the electrolytesolution preparation solvent, to the electrolyte solution material.

The above-mentioned another electrolyte salt is not particularlylimited, and may be any one of the conventional known electrolytes thatmay be used in electrolytes for lithium ion secondary batteries. Asanother electrolyte salt, such an electrolyte salt is exemplified by aninorganic cation salt and organic cation salt oftrifluoromethanesulfonate ion (CF₃SO₃ ⁻), hexafluorophosphate ion (PF₆),perchlorate ion (ClO₄ ⁻), tetrafluoroborate ion (BF₄ ⁻),hexafluoroarsenate ion (AsF₆ ⁻), tetracyanoborate ion ([B(CN)₄]⁻),tetrachloroaluminum ion (AlCl₄ ⁻), tricyanomethide ion (C[(CN)₃]⁻),dicyanamide ion (N[(CN)₂]⁻), tris(trifluoromethanesulfonyl)methide ion(C[(CF₃SO₂)₃]⁻), hexafluoroantimonate ion (SbF₆ ⁻) and dicyanotriazolateion (DCTA) as an anion. Specific examples include LiPF₆, LiPF₃(C₂F₅)₃,LiBF₄, LiBF(CF₃)₃, preferably LiPF₆ or LiBF₄, and more preferably LiPF₆.When the electrolyte solution preparation solvent and theabove-mentioned another electrolyte salt are mixed with the electrolytesolution material according to the present invention to produce thenon-aqueous electrolyte solution, the generation of heat during themixing of the electrolyte salt can be prevented, and therefore thedecomposition of the non-aqueous electrolyte solution can be prevented,resulting in the production of the electrolyte solution having goodquality.

The non-aqueous electrolyte solution according to the present inventionmay contain an additive for improving various properties of a lithiumion secondary battery. The additive may be added at any stage in theprocess of the production of the non-aqueous electrolyte solution, andthe stage is not limited particularly. For example, the additive can beadded after the addition of the electrolyte salt.

The present invention also includes, within the scope thereof: a methodfor storing the electrolyte solution material according to the presentinvention; and a method for transporting the electrolyte solutionmaterial according to the present invention. The electrolyte solutionmaterial according to the present invention contains thefluorosulfonylimide salt represented by general formula (1) and theelectrolyte solvent, wherein the concentration of thefluorosulfonylimide salt represented by general formula (1) is 30% bymass or more. In this case, good stability can be achieved and thegeneration of HF (hydrofluoric acid), which can cause the corrosion of acontainer for storage or transport use, can be prevented. Therefore, theelectrolyte solution material is also suitable for the storage andtransport of the fluorosulfonylimide salt represented by general formula(1). The concentration of the fluorosulfonylimide salt represented bygeneral formula (1) in the electrolyte solution material is preferably35% by mass or more, more preferably 40% by mass or more, still morepreferably not less than 50% by mass or more. The upper limit of theconcentration is preferably 95% by mass or less, more preferably 90% bymass or less. If the concentration of the fluorosulfonylimide saltrepresented by general formula (1) in the electrolyte solution materialis less than 30% by mass, the fluorosulfonylimide salt is decomposed togenerate an acid such as HF, leading to the corrosion of a container orthe deterioration of the electrolyte solution material.

The container to be used for the storage or transport of the electrolytesolution material according to the present invention is not particularlylimited with respect to the form thereof, including the size, materialand the like thereof, and the conventionally known knowledge can applyarbitrary to the container. In the case where a small amount of theelectrolyte solution material synthesized at a laboratory level is to bestored, a small storage container may be used. In the case where a largeamount of the electrolyte solution material synthesized at an industriallevel is to be stored, a large storage container may be used.

As the material for the storage container, a metallic material, such asstainless steel and hastelloy, and a fluorine-based resin, such aspolytetrafluoroethylene (PTFE), and the like can be employed. Amongthese materials, from the viewpoint of having a high pressure-resistingcapacity, it is preferred that the container is made from stainlesssteel. In order to further improve the corrosion resistance of thestorage container, it is preferred to coat the inner surface of acontainer that is made from a material such as the above-mentioned metalwith a resin. In this case, the resin to be used for the coating is notparticularly limited. Specific examples of the resin include: afluorine-based resin, such as polytetrafluoroethylene (PTFE), atetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) and atetrafluoroethylene-hexafluoropropylene copolymer (FEP); and anolefin-based resin, such as polypropylene. From the viewpoint ofachieving an excellent corrosion resistance improving effect, it ispreferred to coat with PTFE. The coating thickness of the resin coatingis not particularly limited, and is preferably 10 to 3000 μm, morepreferably 500 to 1000 μm. It is also preferred for the storagecontainer to be hermetically sealable. An example of the means forenabling the hermetic sealing of the container is an embodiment in whicha valve is provided at a part of the container.

The present application claims the benefit of the priority dates ofJapanese patent application No. 2014-204815 filed on Oct. 3, 2014, andJapanese patent application No. 2015-118065 filed on Jun. 11, 2015. Allof the contents of the Japanese patent application No. 2014-204815 filedon Oct. 3, 2014, and Japanese patent application No. 2015-118065 filedon Jun. 11, 2015, are incorporated by reference herein.

EXAMPLES

Hereinafter, the present invention is described in detail with Examples.However, the present invention is not limited to the following Examplesin any way, and it is possible to carry out the present inventionaccording to the Examples with an additional appropriate change withinthe range of the above descriptions and the following descriptions. Sucha change is also included in the technical scope of the presentinvention.

[Amount of Residual Solvent]

A measurement solution was prepared by adding 200 μl of an aqueousdimethyl sulfoxide solution (dimethyl sulfoxide/ultrapure water=20/80 byvolume) and 2 ml of a 20 mass % aqueous sodium chloride solution to 0.05g of an electrolyte solution material. The measurement solution wasplaced in a vial bottle, and the vial bottle was hermetically sealed.The amount of a residual solvent contained in the electrolyte solutionmaterial was measured with a headspace gas chromatography system(“Agilent6890”, manufactured by Agilent).

Device: Agilent 6890

Column: HP-5 (length: 30 m, column inner diameter: 0.32 mm, filmthickness: 0.25 μm) (manufactured by Agilent)

Column temperature conditions: 60° C. (retained for 2 minutes),temperature was raised to 300° C. at 30° C./min, 300° C. (retained for 2minutes)

Headspace conditions: 80° C. (retained for 30 minutes)

Injector temperature: 250° C.

Detector: FID (300° C.)

Production Example 1: Production of Lithium di(fluorosulfonyl)imide(LiFSI)

Into a 500-mL PFA-made reaction container equipped with a stirrer and acondenser, 120 g of butyl acetate was introduced. Subsequently, 16.1 gof di(chlorosulfonyl)imide (75 mmol) was further introduced into thereaction container. The resultant solution was stirred to dissolve thecompounds. To the resultant di(chlorosulfonyl)imide solution, 4.45 g ofammonium chloride (82.5 mmol) was added, and the solution was stirred at80° C. for 1 hour. Acidic ammonium fluoride NH₄F.HF (20.53 g) (360 mmol)was added to the di(chlorosulfonyl)imide solution, and the resultantsolution was further stirred at 80° C. for 4 hours.

After the completion of the reaction, the reaction solution was cooledto room temperature, and then a solid material was removed byfiltration. The filtrate was transferred to a separating funnel, then anaqueous solution prepared by dissolving 3.15 g (75 mmol) of lithiumhydroxide monohydrate in 21 g of ultrapure water was added thereto, andthe resultant solution was agitated. After the resultant solution wasallowed to stand, an aqueous layer was removed. An aqueous solutionprepared by dissolving 1.57 g (37 mmol) of lithium hydroxide monohydratein 11 g of ultrapure water was added again to the resultant solution,and the solution was stirred. After the resultant solution was allowedto stand, an aqueous layer was removed.

As an organic layer, 128 g of a solution containing 10 g of lithiumdi(fluorosulfonyl)imide was obtained. The obtained solution was heatedat 50° C. and 1.5 kPa for 1 hour to volatilize butyl acetate, therebyproducing 30 g of a solution composed of 10 g of lithiumdi(fluorosulfonyl) and 20 g of butyl acetate. By the use of a ¹⁹F-NMR(solvent: deuterated acetonitrile) measurement, the amount of lithiumdi(fluorosulfonyl)imide contained in the organic layer was determinedfrom the amount of trifluoromethylbenzene, which was added as aninternal standard substance, and the comparison between an integralvalue of a peak derived from the internal standard substance and anintegral value of a peak derived from the desired product.

Example 1

A lithium di(fluorosulfonyl)imide powder (4.99 g) containing butylacetate (208 ppm) and dichloromethane (4621 ppm), which was preparedseparately, and diethyl carbonate (7.56 g) were placed in a 50-mleggplant flask, and the mixture was dissolved. The solution wasdecompressed at 25° C. and 1 kPa for 3 hours to volatilize the solvent.In this manner, 11.64 g diethyl carbonate solution of lithiumdi(fluorosulfonyl)imide was produced as an electrolyte solutionmaterial. The solution thus produced contained butyl acetate at aconcentration of 83 ppm, but the presence of dichloromethane was notconfirmed. Dichloromethane, which had low affinity for lithiumdi(fluorosulfonyl)imide, was reduced through the volatilization step.

Example 2

In a 25-ml eggplant flask, ethylene carbonate (EC) (4.76 g) was added toa lithium di(fluorosulfonyl)imide powder (3.23 g) containing butylacetate (208 ppm) and dichloromethane (4621 ppm), thereby the mixturewas dissolved. The solution was decompressed at 25° C. and 1 kPa for 3hours to volatilize the solvent. In this manner, 7.83 g of an ethylenecarbonate solution of lithium di(fluorosulfonyl)imide was produced as anelectrolyte solution material. It was confirmed that the solution thusproduced contained 85 ppm of butyl acetate and 40 ppm ofdichloromethane.

Example 3

Into a 100-ml eggplant flask, a solution prepared by dissolving 10 g oflithium di(fluorosulfonyl)imide in 20 g of butyl acetate and 20 g ofethylene carbonate were introduced. The solution was heated anddecompressed at 60° C. and 1.5 kPa for 8 hours to volatilize thesolvent. In this manner, 28 g of a solution of lithiumdi(fluorosulfonyl)imide in ethylene carbonate was produced as anelectrolyte solution material. It was confirmed that the solution thusproduced contained 60 ppm of butyl acetate. Butyl acetate, which hadmoderate affinity for lithium di(fluorosulfonyl)imide, was reducedthrough the volatilization step.

Examples 4-1 to 7-5

The same procedure as in Example 3 was carried out, except that thesolvent to be contained in the di(fluorosulfonyl)imide solution, theelectrolyte solution solvent, the temperature of the solution, thedegree of reduction in pressure and the heating time were changed asshown in Tables 1 to 4. In this manner, electrolyte solution materialseach containing di(fluorosulfonyl)imide were produced. The amounts ofthe residual solvents in the individual solutions are shown in thetables.

Examples 8-1 to 8-3

The same procedure as in Example 3 was carried out, except that asolution composed of 10 g of lithium di(fluorosulfonyl)imide produced inProduction Example 1 and 20 g of butyl acetate was used and thetemperature of the solution, the degree of reduction in pressure and theheating time were changed as shown in Table 5. In this manner,electrolyte solution materials each containing di(fluorosulfonyl)imidewere produced. The amounts of the residual solvents in the individualsolutions are shown in the table.

Examples 9-1 to 13-5

The same procedure as in Example 3 was carried out, except that thesolvent to be contained in the di(fluorosulfonyl)imide solution, theelectrolyte solution solvent, the temperature of the solution, thedegree of reduction in pressure and the heating time were changed asshown in Tables 6 to 10. In this manner, electrolyte solution materialseach containing di(fluorosulfonyl)imide were produced. The amounts ofthe residual solvents in the individual solutions are shown in thetables.

TABLE 1 Example 4-1 4-2 4-3 4-4 4-5 4-6 Solvent AcetonitrileAcetonitrile Acetonitrile Acetonitrile Acetonitrile Acetonitrile Solventweight/g 20 20 20 20 20 10 Electrolyte solution solvent PropyleneEthylene γ-butyloractone Diethyl Ethyl methyl Dimethyl carbonatecarbonate carbonate carbonate carbonate Used amount of 20 20 20 20 20 20electrolyte solution solvent Heating temperature/° C. 50 50 50 50 50 40Degree of reduction 1.5 1.5 1.5 1.5 3 3 in pressure/kPa Heateing time/hr4 4 4 4 3 2 Yeild of 29.9 29.8 28 34 33 21 electrolyte solutionmaterial/g Residual solvent/ppm 30 30 40 290 610 1900

TABLE 2 Example 5-1 5-2 5-3 Solvent Benzonitrile BenzonitrileBenzonitrile Solvent weight/g 20 20 20 Electrolyte solution solventPropylene Ethylene γ- carbonate carbonate butyloractone Used amount ofelectrolyte 20 20 20 solution solvent Heating temperature/° C. 100 100100 Degree of reduction in 1.5 1.5 1.5 pressure/kPa Heateing time/hr 8 88 Yeild of electrolyte solution 32 32 30 material/g Residual solvent/ppm630 630 630

TABLE 3 Example 6-1 6-2 6-3 6-4 6-5 6-6 6-7 Solvent Ethyl acetate Ethylacetate Ethyl acetate Ethyl acetate Ethyl acetate Ethyl acetate Ethylacetate Solvent weight/g 20 20 20 20 20 20 20 Electrolyte solutionsolvent Propylene Ethylene γ-butyloractone Diethyl Ethyl methyl Diethyl1,2- carbonate carbonate carbonate carbonate carbonate dimethoxyethaneUsed amount of 20 20 20 20 20 20 20 electrolyte solution solvent Heatingtemperature/° C. 40 40 40 40 40 40 40 Degree of reduction 1.5 1.5 1.51.5 1.5 1.5 1.5 in pressure/kPa Heateing time/hr 8 8 8 6 3 3 2 Yeild of30 30.1 29.5 30.5 30.5 27.5 23 electrolyte solution material/g Residualsolvent/ppm 50 50 40 120 330 360 560

TABLE 4 Example 7-1 7-2 7-3 7-4 7-5 Solvent Isopropyl IsopropylIsopropyl Isopropyl Isopropyl acetate acetate acetate acetate acetateSolvent weight/g 20 20 20 20 20 Electrolyte solution Propylene Ethyleneγ- Diethyl Ethyl methyl solvent carbonate carbonate butyloractonecarbonate carbonate Used amount of electrolyte 20 20 20 20 20 solutionsolvent Heating temperature/° C. 40 40 40 40 40 Degree of reduction in 33 3 30 30 pressure/kPa Heateing time/hr 8 8 8 6 2 Yeild of electrolyte29.7 29.8 28 30.3 28 solution material/g Residual solvent/ppm 10 10 20330 980

TABLE 5 Example 8-1 8-2 8-3 Solvent Butyl acetate Butyl acetate Butylacetate Solvent weight/g 20 20 20 Electrolyte solution solvent PropyleneEthylene γ- carbonate carbonate butyloractone Used amount of electrolyte20 20 20 solution solvent Heating temperature/° C. 60 60 60 Degree ofreduction in 1.5 1.5 1.5 pressure/kPa Heateing time/hr 8 8 8 Yeild ofelectrolyte 28 28 27 solution material/g Residual solvent/ppm 40 60 80

TABLE 6 Example 9-1 9-2 9-3 9-4 9-5 9-6 9-7 9-8 Solvent Diethyl etherDiethyl ether Diethyl ether Diethyl ether Diethyl ether Diethyl etherDiethyl ether Diethyl ether Solvent weight/g 20 20 20 20 20 20 20 20Electrolyte solution solvent Propylene Ethylene γ-butyloractone DiethylEthyl methyl Dimthyl 1,2- Methyl carbonate carbonate carbonate carbonatecarbonate dimethoxyetha propionate Used amount of 20 20 20 20 20 20 2020 electrolyte solution solvent Heating temperature/° C. 35 35 35 35 3535 35 35 Degree of reduction 15 15 15 15 15 15 15 15 in pressure/kPaHeateing time/hr 4 4 4 4 4 4 4 4 Yeild of 30 30 30 30 30 30 30 30electrolyte solution material/g Residual solvent/ppm 0 0 0 0 0 0 0 0

TABLE 7 Example 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 SolventDiisopropyl Diisopropyl Diisopropyl Diisopropyl Diisopropyl DiisopropylDiisopropyl ether Diethyl ether ether ether ether ether ether etherSolvent weight/g 20 20 20 20 20 20 20 20 Electrolyte solution solventPropylene Ethylene γ-butyloractone Diethyl Ethyl methyl Dimthyl 1,2-Methyl carbonate carbonate carbonate carbonate carbonate dimethoxyethanepropionate Used amount of 20 20 20 20 20 20 20 20 electrolyte solutionsolvent Heating temperature/° C. 45 45 45 45 45 45 45 45 Degree ofreduction 5 5 5 5 5 5 5 5 in pressure/kPa Heateing time/hr 3 3 3 3 3 3 33 Yeild of electrolyte solution 30 30 30 29.5 29.3 28 25 24 material/gResidual solvent/ppm 20 20 20 150 300 1500 2000 2500

TABLE 8 Example 11-1 11-2 11-3 11-4 11-5 11-6 11-7 11-8 Solvent t-butylt-butyl t-butyl t-butyl t-butyl t-butyl t-butyl t-butyl methyl methylmethyl methyl methyl methyl methyl methyl ether ether ether ether etherether ether ether Solvent weight/g 20 20 20 20 20 20 20 20 Electrolytesolution solvent Propylene Ethylene γ-butyl- Diethyl Ethyl Dimethyl1,2-dimethoxy- Methyl carbonate carbonate oractone carbonate methylcarbonate ethane propionate carbonate Used amount of 20 20 20 20 20 2020 20 electrolyte solution solvent Heating temperature/° C. 35 35 35 3535 35 35 35 Degree of reduction 15 15 15 15 15 15 15 15 in pressure/kPaHeateing time/hr 4 4 4 4 4 4 4 4 Yeild of 30 30 30 30 30 30 30 30electrolyte solution material/g Residual solvent/ppm 0 0 0 0 0 0 0 0

TABLE 9 Example 12-1 12-2 12-3 12-4 Solvent Cyclopentyl CyclopentylCyclopentyl Cyclopentyl methyl methyl methyl methyl ether ether etherether Solvent weight/g 20 20 20 20 Electrolyte Propylene Ethylene γ-Diethyl solution solvent carbonate carbonate butyloractone carbonateUsed amount of 20 20 20 20 electrolyte solution solvent Heating 55 55 5555 temperature/° C. Degree of 2.5 2.5 2.5 2.5 reduction in pressure/kPaHeateing time/hr 3 3 3 3 Yeild of 30 30 30 28 electrolyte solutionmaterial/g Residual 40 60 70 800 solvent/ppm

TABLE 10 Example 13-1 13-2 13-3 13-4 13-5 Solvent NitromehtaneNitromehtane Nitromehtane Nitromehtane Nitromehtane Solvent weight/g 2020 20 20 20 Electrolyte Propylene Ethylene γ- Diethyl Ethyl mehylsolution solvent carbonate carbonate butyloractone carbonate carbonateUsed amount of 20 20 20 20 20 electrolyte solution solvent Heating 55 5555 55 55 temperature/° C. Degree of 2 2 2 2 2 reduction in pressure/kPaHeateing time/hr 3 3 3 3 3 Yeild of 30 30 30 28 27 electrolyte solutionmaterial/g Residual 50 40 70 800 900 solvent/ppm

Comparative Example 1

A lithium di(fluorosulfonyl)imide powder (5 g) containing 208 ppm ofbutyl acetate and 4621 ppm of dichloromethane was spread on a petri dishand then dried in a vacuum drier at 60° C. and 1 kPa for 12 hours.However, the amounts of the residual solvents were not reduced.

Comparative Example 2

A lithium di(fluorosulfonyl)imide powder (5 g) containing 208 ppm ofbutyl acetate and 4621 ppm of was ground with a mortar. The groundproduct was spread on a petri dish and was then dried in a vacuum drierat 60° C. and 1 kPa for 12 hours. However, the amounts of the residualsolvents were not reduced.

Example 15-1

A lithium di(fluorosulfonyl)imide powder (5.00 g) containing 208 ppm ofbutyl acetate and 4621 ppm of dichloromethane which were residualsolvents was introduced into a 50-ml eggplant flaks. EC (5.10 g) wasfurther added to the powder, thereby the mixture was dissolved. Thesolution was heated at 60° C. and 1 kPa for 3 hours to volatilize thesolvent. In this manner, an electrolyte solution material composed of5.00 g of LiFSI and 5.00 g of EC was produced.

The amounts of the residual solvents immediately after the production ofthe electrolyte solution material were as follows: butyl acetate: 55ppm, dichloromethane: 5 ppm, water: 20 ppm, and HF: 4 ppm. Theelectrolyte solution material was stored in a stainless steel-madecontainer at 60° C. for 30 days. The amount of HF in the electrolytesolution material after the storage was 8 ppm. This fact means that 4ppm of HF was generated during storage. This amount was converted to anamount per mass of lithium di(fluorosulfonyl)imide (LiFSI), and theconverted amount was 8 ppm/LiFSI-kg.

The determination of amount of HF was carried out using an automatictitrator manufactured by Metrohm. Specifically, neutralization titrationwas carried out with a 0.01-N sodium hydroxide/methanol solution using asolvotrode electrode for non-aqueous media. The conversion of the amountof the acid was carried out in terms of HF.

Example 15-2

Into a 50-ml eggplant flaks, 5.00 g of a lithium di(fluorosulfonyl)imidepowder containing butyl acetate (208 ppm) and dichloromethane (4621 ppm)which were residual solvents was introduced. EC (1.98 g) was furtheradded to the powder, thereby the mixture was dissolved. The solution washeated at 60° C. and 1 kPa for 3 hours to volatilize the solvent. Inthis manner, a solution composed of 5.00 g of LiFSI and 1.78 g of EC wasproduced. Subsequently, 3.22 g of ethyl methyl carbonate (EMC) was addedto the solution to produce an electrolyte solution material. The amountsof the residual solvents in the electrolyte solution materialimmediately after the preparation were as follows: butyl acetate: 45ppm, and dichloromethane: 6 ppm. Subsequently, the amounts of HF andothers before and after the storage were determined in the same manneras in Example 15-1.

Example 15-3

Into a 50-ml eggplant flaks, 5.00 g of a lithium di(fluorosulfonyl)imidepowder containing 208 ppm of butyl acetate and 4621 ppm ofdichloromethane which were residual solvents was introduced. EC (4.50 g)was further added to the powder, thereby the mixture was dissolved. Thesolution was heated at 60° C. and 1 kPa for 3 hours to volatilize thesolvent. In this manner, a solution composed of 5.00 g of LiFSI and 4.40g of EC was produced. Subsequently, 0.6 g of ethyl methyl carbonate(EMC) was added to the solution to produce an electrolyte solutionmaterial. The amounts of the residual solvents in the electrolytesolution material immediately after the preparation were as follows:butyl acetate: 43 ppm, and dichloromethane: 5 ppm. Subsequently, theamounts of HF and others before and after the storage were determined inthe same manner as in Example 15-1.

Example 15-4

Into a 50-ml eggplant flaks, 5.00 g of a lithium di(fluorosulfonyl)imidepowder containing 208 ppm of butyl acetate and 4621 ppm ofdichloromethane which were residual solvents was introduced.γ-Butyrolactone (GBL, 5.20 g) was further added to the powder, therebythe mixture was dissolving the powder in GBL. The solution was heated at60° C. and 1 kPa for 3 hours to volatilize the solvent. In this manner,a solution composed of 5.00 g of LiFSI and 5.00 g of GBL was produced.The amounts of the residual solvents in the electrolyte solutionmaterial immediately after the preparation were as follows: butylacetate: 85 ppm, and dichloromethane: 9 ppm. Subsequently, the amountsof HF and others before and after the storage were determined in thesame manner as in Example 15-1.

Example 15-5

Into a 50-ml eggplant flaks, 6.20 g of a lithium di(fluorosulfonyl)imidepowder 208 ppm of containing butyl acetate and 4621 ppm ofdichloromethane which were residual solvents was introduced. Further,4.00 g of EC was added to the powder, thereby the mixture was dissolved.The solution was heated at 60° C. and 1 kPa for 3 hours to volatilizethe solvent. In this manner, a solution composed of 6.20 g of LiFSI and3.80 g of EC was produced. The amounts of the residual solvents in theelectrolyte solution material immediately after the preparation were asfollows: butyl acetate: 78 ppm, and dichloromethane: 7 ppm.Subsequently, the amounts of HF and others before and after the storagewere determined in the same manner as in Example 15-1.

Example 15-6

Into a 50-ml eggplant flaks, 6.20 g of a lithium di(fluorosulfonyl)imidepowder containing 208 ppm of butyl acetate and 4621 ppm ofdichloromethane which were residual solvents was introduced. Further,1.50 g of EC was added to the powder, thereby the mixture was dissolved.The solution was heated at 60° C. and 1 kPa for 3 hours to volatilizethe solvent. In this manner, a solution composed of 6.20 g of LiFSI and1.35 g of EC was produced. Subsequently, 2.45 g of ethyl methylcarbonate (EMC) was added to the solution to produce an electrolytesolution material. The amounts of the residual solvents in theelectrolyte solution material immediately after the preparation were asfollows: butyl acetate: 95 ppm, and dichloromethane: 10 ppm.Subsequently, the amounts of HF and others before and after the storagewere determined in the same manner as in Example 15-1.

Reference Example 1

A solution composed of 5.00 g of LiFSI and 5.00 g of EC was produced inthe same manner as in Example 15-1. EC was further added to the powder,thereby producing an EC solution containing 10.2% by mass of LiFSI. Theamounts of the residual solvents in the solution were as follows: butylacetate: 13 ppm, and dichloromethane: 2 ppm. The amounts of HF andothers before and after the storage were determined in the same manneras in Example 15-1.

Reference Example 2

A solution composed of 5.00 g of LiFSI, 1.78 g of EC and 3.22 g of EMCwas produced in the same manner as in Example 15-2. Further, 25.12 g ofEC was added to the powder, thereby producing an EC solution containing10.2% by mass of LiFSI. The amounts of the residual solvents in thesolution were as follows: butyl acetate: 14 ppm, and dichloromethane: 1ppm. The amounts of HF and others before and after the storage weredetermined in the same manner as in Example 15-1.

TABLE 11 Reference Experimental example example Unit 15-1 15-2 15-3 15-415-5 15-6 1 2 EC mass % 50 38 89.8 EC/EMC = 85/15 mass % 50 EC/EMC = 3/7mass % 50 38 89.8 GBL mass % 50 LiFSI mass % 50 50 50 50 62 62 10.2 10.2Initial concentration of HF ppm 4 5 5 4 6 5 4 5 HF concentration ppm 810 10 8 10 9 16 17 after storage at 60° C. for 30 Increasing amount ofHF ppm 4 5 5 4 4 4 12 12 HF amount per mass of LiFSI ppm/LiFSI-kg 8 9 98 7 6 74 79 Residual solvent ppm 55 45 43 85 78 95 13 14 Butyl acetateResidual solvent ppm 5 6 5 9 7 10 2 1 Diclrolomethane

As shown in Table 11, in each of Reference Examples, when compared withExamples 15-1 to 15-6 in each of which the concentration of LiFSI in theelectrolyte solution material was not less than 50% by mass, it wasdemonstrated that the concentration of LiFSI in the electrolyte solutionmaterial was 10.2% by mass but the amount of HF generated during thestorage was significant. Consequently, it was confirmed that all of theelectrolyte solution materials according to the present invention, eachcontaining LiFSI in an amount not less than a specific amount, had aneffect of inhibiting the generation of HF during storage.

Example A-1

The same procedure as in Example 2 was carried out, except that theamount of ethylene carbonate used in Example 2 was changed to 4.60 g. Inthis manner, an electrolyte solution material was produced. Further,2.62 g of LiPF₆, 5.69 g of EC and 18.40 g of ethyl methyl carbonate(EMC) were added to the electrolyte solution material to produce anon-aqueous electrolyte solution which contained 9.3% by mass (0.6 M) oflithium di(fluorosulfonyl)imide and 67.5% by mass (0.6 M) of LiPF₆ in anEC/EMC (=3/7 (by volume)) mixed solvent. The amounts of the residualsolvents in the non-aqueous electrolyte solution were as follows: butylacetate: 8 ppm, and dichloromethane: 4 ppm.

Example A-2

The same procedure as in Example A-1 was carried out, except that theconditions employed for volatilizing the residual solvents in ExampleA-1 were changed to 25° C., 40 kPa and 3 hours. In this manner, anelectrolyte solution material was produced. The amounts of the residualsolvents in the electrolyte solution material were as follows: butylacetate: 96 ppm, and dichloromethane: 308 ppm. To the electrolytesolution material were further added LiPF₆, EC and EMC in the sameamounts as in Example A-1. In this manner, a non-aqueous electrolytesolution was produced, which contained 9.3% by mass (0.6 M) of LiFSI and67.5% by mass (0.6 M) of LiPF₆ in an EC/EMC (=3/7 (by volume)) mixedsolvent. The amounts of the residual solvents in the non-aqueouselectrolyte were as follows: butyl acetate: 9 ppm, and dichloromethane:29 ppm.

Example A-3

The same procedure as in Example A-1 was carried out, except that theconditions employed for volatilizing the residual solvents in ExampleA-1 were changed to 25° C., 100 kPa and 3 hours. In this manner, anelectrolyte solution material was produced. The amounts of the residualsolvents in the electrolyte solution material were as follows: butylacetate: 150 ppm, and dichloromethane: 1280 ppm. To the electrolytesolution material were further added LiPF₆, EC and EMC in the sameamounts as in Example A-1. In this manner, a non-aqueous electrolytesolution was produced, which contained 9.3% by mass (0.6 M) of LiFSI and67.5% by mass (0.6 M) of LiPF₆ in an EC/EMC (=3/7 (by volume)) mixedsolvent. The amounts of the residual solvents in the non-aqueouselectrolyte were as follows: butyl acetate: 19 ppm, and dichloromethane:119 ppm.

Comparative Example A-1

The same procedure as in Example A-1 was carried out, except that theoperation for volatilizing the residual solvents was not carried out. Inthis manner, an electrolyte solution material was produced. The amountsof the residual solvents in the electrolyte solution material are asfollows: butyl acetate: 208 ppm, and dichloromethane: 4621 ppm. To theelectrolyte solution material were further added LiPF₆, EC and EMC inthe same amounts as in Example A-1. In this manner, a non-aqueouselectrolyte solution was produced, which contained 9.3% by mass (0.6 M)of LiFSI and 67.5% by mass (0.6 M) of LiPF₆ in an EC/EMC (=3/7 (byvolume)) mixed solvent. The amounts of the residual solvents in thenon-aqueous electrolyte solution were as follows: butyl acetate: 17 ppm,and dichloromethane: 430 ppm.

As shown in Table 12, in each of Examples A-1 to A-3, the volumeexpansion of the battery after being stored at 60° C. for 1 month wasabout 0.03 to 0.06 ml. In Comparative Example A-1, in contrast, theresult was 0.21 ml. It was confirmed that, in a battery which wasprovided with a non-aqueous electrolyte solution produced using anelectrolyte solution material having a reduced residual solvent amount,the swelling of the battery was prevented during the charge-dischargeoperation of the battery.

Production of Laminate-Type Lithium Ion Secondary Battery

1. Production of Positive Electrode Sheet

A positive electrode active material (LiCoO₂), a conduction-assistingagent 1 (acethylene black, AB), a conduction-assisting agent 2(graphite) and a binder (polyvinylidene fluoride, PVdF) were mixedtogether at a mixing ratio of 92:2:2:4 by mass. A positive electrode mixslurry, which was prepared by dispersing the mixture inN-methylpyrrolidone, was applied onto an aluminum foil, and was thendried and compressed to produce a positive electrode sheet.

2. Production of Negative Electrode Sheet

A negative electrode active material (graphite), a conduction-assistingagent (VGCF) and binders (SBR+CMC) were mixed together at a mixing ratioof 97:0.5:2.5 by mass, and then the mixture was mixed withN-methylpyrrolidone to produce a negative electrode mix slurry. Thecharging capacity of the positive electrode when charged at 4.2 V wascalculated, and the negative electrode mix slurry was applied onto acopper foil (a negative electrode current collector) in such a mannerthat the (lithium ion storable capacity of negative electrode)/(chargingcapacity of positive electrode) ratio became 1.1. The resultant productwas dried and then compressed to produce a negative electrode sheet.

3. Production of Laminate-Type Lithium Ion Secondary Battery

An aluminum tab and a nickel tab were welded to a non-coated portion ofeach of one sheet of the above-produced positive electrode sheet and onesheet of the above-produced negative electrode sheet, and then theseelectrode sheets were allowed to face each other with apolyethylene-made separator interposed therebetween. The resultantproduct was wound with a winder to produce a wound article. The woundarticle was sandwiched between an aluminum laminate film which wasalready subjected to a drawing press processing at a proper depth and anuntreated aluminum laminate film, and the inside of each of the aluminumlaminate films was filled with a mixed solvent electrolyte solutionproduced in each of examples A-1 to A-3 and Comparative Example A-1. Theresultant product was hermetically sealed under vacuum conditions toproduce a laminate-type lithium ion secondary battery having a capacityof 1 Ah.

4. Evaluation of Battery

Specific Capacity (mAh/g)

The laminate-type lithium ion secondary battery was charged for 5 hoursunder specific charging conditions (0.5 C, 4.2 V, a constantcurrent/constant voltage mode) under an environment at a temperature of25° C. using a charge-discharge tester (ACD-01, manufactured by AskaElectronic Co., Ltd.; the same tester was used in the followingprocedures). Subsequently, the battery was discharged under specificdischarging conditions (0.2 C, discharge termination voltage: 3.0 V, aconstant current discharging mode). The first-round discharge capacitywas recorded, and the specific capacity on mass basis of the battery wascalculated in accordance with the equation shown below. In this manner,the initial discharge property was evaluated. Specific capacity on massbasis (mAh/g)=(first-round charge capacity of battery (mAh))/(mass (g)of positive electrode active material)

5. Storage Properties at High Temperature]

After the measurement of the specific capacity, the laminate-typelithium ion secondary battery was charged under specific chargingconditions (1 C, 4.2 V, or cut off 0.02 C in a constant current/constantvoltage mode) under an environment at a temperature of 25° C. using acharge-discharge tester. Subsequently, the battery was discharged underspecific discharging conditions (0.2 C, discharge termination voltage:3.0 V, a constant current discharging mode), and was then charged againunder specific charging conditions (1 C, 4.2 V, cut off 0.02 C in aconstant current/constant voltage mode). A cell thus produced was storedin a thermostatic chamber at 60° C. for 1 month. The cell before andafter the storage was immersed in water, and the volume of the cellbefore the storage and the volume of the cell after the storage weremeasured. From the difference between the volume of the cell before thestorage and the volume of the cell after the storage, the amount ofswelling of the cell after the storage was determined. The results areshown in Table 12.

TABLE 12 Residual solvent Residual amount in solvent electrolyte amountin solution electrolyte Volume material solution expansion Volatil- ppmppm at 60° C. ization Butyl Dicloro- Butyl Dicloro- for one conditionacetate methane acetate methane month ml Example  1 kPa 85 40 8 4 0.03A-1 Example  40 kPa 96 308 9 29 0.03 A-2 Example 100 kPa 150 1280 17 1190.06 A-3 Compar- none 208 4621 19 430 0.21 ative example A-1

Example B-1

Materials were introduced into a mixing tank in the order ofintroduction shown in Table 13 to produce a non-aqueous electrolytesolution. In the table, LiFSI and EC, of each of which the order ofintroduction was “1”, were used in the form of an electrolyte solutionmaterial that was prepared previously by mixing 11.22 kg of LiFSI with36.36 kg of EC. The electrolyte solution material was introduced intothe mixing tank (capacity: 150 L), and then 27.82 kg of EMC and 35.81 kgof diethyl carbonate (sometimes abbreviated as “DEC”, hereinafter),which served as electrolyte solution preparation solvents, and 9.12 kgof LiPF₆ (manufactured by Kishida Chemical Co., Ltd.), which served asthe above-mentioned another electrolyte salt, were introduced into themixing tank in this order. The resultant mixture was stirred for 10minutes to produce a non-aqueous electrolyte solution. In this regard,10 minutes was required for the introduction of each of the electrolytesolution material, the electrolyte solution preparation solvents and theabove-mentioned another electrolyte salt. In the table, “required time”is a time from the initiation of the introduction to the termination ofthe introduction. The introduction of each of the materials was carriedout while stirring. The liquid temperature after the introduction ofeach of the materials into the mixing tank was measured, and the resultsare shown in Table 13. In other Examples, the measurement of thetemperature was carried out in the same manner.

TABLE 13 Required Liquid temperature Order of Introduced Amount ofintroduction Input ratio* time after introduction introduction materialsMw Specific gravity mol kg L (volume) (minute) (° C.) 1 LiFSI 187 2.320.6 11.22 4.8 10 25 EC 1.32 36.36 27.54 3 2 EMC 1.01 27.82 27.54 3 10 3DEC 0.975 35.81 36.72 4 10 4 LiPF₆ 152 2.72 0.6 9.12 3.4 10 45 — — — — —— — — 10 TOTAL 120.3 100 50 *“Input ratio” represents the ratio of theintroduced amount of EC, EMC and DEC.

As shown in Table 13, the liquid temperature in the mixing tank wasmeasured in the course of the production of the non-aqueous electrolyte,the liquid temperature never exceeded 60° C. Specifically, thegeneration of heat did not occur upon the introduction of theelectrolyte solution preparation solvents (EMC, DEC) into theelectrolyte solution material. After the introduction of LiPF₆, theliquid temperature increased 45° C., but the decomposition of theelectrolyte did not occur.

Example B-2

Materials were introduced into a mixing tank in the order ofintroduction shown in Table 14 to produce a non-aqueous electrolytesolution. Specifically, an electrolyte solution material prepared bymixing 11.22 kg of LiFSI with 20.0 kg of EC was introduced into themixing tank (capacity: 150 L), and then 27.82 kg of EMC and 35.81 kg ofDEC, which served as electrolyte solution preparation solvents, wereintroduced into the mixing tank. Subsequently, 16.36 kg of EC whichserved as an electrolyte solution preparation solvent and was heated to60° C. was introduced into the mixing tank, and then 9.12 kg of LiPF₆which served as the above-mentioned another electrolyte salt wasintroduced thereinto. The resultant solution was stirred for 10 minutesto produce a non-aqueous electrolyte solution. In this regard, 10minutes was required for the introduction of each of the electrolytesolution material, the electrolyte solution preparation solvents and theabove-mentioned another electrolyte salt.

TABLE 14 Required Liquid temperature Order of Introduced Amount ofintroduction Input ratio time after introduction introduction materialsMw Specific gravity mol kg L (volume) (minute) (° C.) 1 LiFSI 187 2.320.6 11.22 4.8 10 25 EC 1.32 20.00 15.15 1.65 2 EMC 1.01 27.82 27.54 3 103 DEC 0.975 35.81 36.72 4 10 4 EC 1.32 16.36 12.39 1.35 10 30 5 LiPF₆152 2.72 0.6 9.12 3.4 10 50 — — — — — — — — 10 TOTAL 120.3 100.0 60

The liquid temperature in the mixing tank was measured in the course ofthe production of the non-aqueous electrolyte. The liquid temperaturenever exceeded 60° C. Specifically, the generation of heat did not occurupon the introduction of the electrolyte solution preparation solvents(EMC, DEC) into the electrolyte solution material. The liquidtemperature increased 30° C. after the introduction of EC that washeated to 60° C., and the liquid temperature increased 50° C. after theintroduction of LiPF₆. However, the decomposition of the electrolyte didnot occur.

Comparative Example B-1

Materials were introduced into a mixing tank in the order ofintroduction shown in Table 15 to produce a non-aqueous electrolytesolution. Specifically, 36.36 kg of an EC solution that was heated to60° C. was introduced into the mixing tank, and then 27.82 kg of EMC and35.81 kg of DEC were further introduced thereinto to produce anon-aqueous solvent solution. Subsequently, LiFSI was introduced intothe mixing tank. In this regard, LiFSI was introduced in divided threeportions (11.22 kg/portion) (3.74 kg in total) so as to prevent theliquid temperature from exceeding 55° C. Subsequently, LiPF₆ wasintroduced in divided three portions (9.12 kg/portion) (3.04 kg intotal). After the introduction, the resultant solution was stirred for10 minutes to produce a non-aqueous electrolyte solution. The timerequired for the introduction of each of the electrolyte solutionpreparation solvents, LiFSI and LiPF₆ was 10 minutes. The time requiredfor the introduction of each of LiFSI and LiPF₆ was expressed in thetotal time (10 minutes/portion×3 portions).

TABLE 15 Required Liquid temperature Order of Introduced Amount ofintroduction Input ratio time after introduction introduction materialsMw Specific gravity mol kg L (volume) (minute) (° C.) 1 EC 1.32 36.3627.54 3 10 60 2 EMC 1.01 27.82 27.54 3 10 3 DEC 0.945 35.81 36.72 4 1040 4 LiFSI 187 2.32 0.6 11.22 4.8 30 5 LiPF₆ 152 2.72 0.6 9.12 3.4 30 —— — — — — — — 10 TOTAL 120.33 100 100

The liquid temperature in the mixing tank was measured in the course ofthe production of the non-aqueous electrolyte solution. The liquidtemperature never exceeded 60° C. Specifically, the generation of heatdid not occur upon the introduction of the electrolyte solutionpreparation solvents (EMC, DEC) into the EC solution. The liquidtemperature after the preparation of the non-aqueous solvent solutionwas 40° C. (the order of introduction: 3). Because each of LiFSI andLiPF₆ was subsequently introduced in divided portions, the increase intemperature was prevented and, therefore, the decomposition of thenon-aqueous electrolyte solution did not occur. However, it took longtime to add LiFSI and LiPF₆, and therefore productivity was poor.

Comparative Example B-2

Materials were introduced into a mixing tank in the order ofintroduction shown in Table 16 to produce a non-aqueous electrolytesolution. Specifically, a non-aqueous solvent solution (40° C.) wasprepared in the same manner as in Comparative Example 1, and then 11.22kg of LiFSI was introduced. Subsequently, 9.12 kg of LiPF₆ wasintroduced. After the introduction, the resultant solution was stirredfor 10 minutes to produce a non-aqueous electrolyte solution. In thisregard, 10 minutes was required for the introduction of each of theelectrolyte solution preparation solvents, LiFSI and LiPF₆.

TABLE 16 Required Liquid temperature Order of Introduced Amount ofintroduction Input ratio time after introduction introduction materialsMw Specific gravity mol kg L (volume) (minute) (° C.) 1 EC 1.32 36.3627.54 3 10 60 2 EMC 1.01 27.82 27.54 3 10 3 DEC 0.945 35.81 36.72 4 1040 4 LiFSI 187 2.32 0.66 11.22 4.8 10 55 5 LiPF₆ 152 2.72 0.6 9.12 3.410 75 — — — — — — — — 10 TOTAL 120.3 8.2 60

The liquid temperature after the introduction of LiFSI increased to 55°C., and the liquid temperature after the introduction of LiPF₆ increaseto 75° C. The non-aqueous electrolyte solution was discolored in paleorange, and the decomposition of the electrolyte occurred.

From the results of Examples B-1, B-2 and Comparative Examples B-1 andB-2, the following thing is demonstrated. As shown in Examples B-1 andB-2, when the electrolyte solution material which was preparedpreviously by mixing the fluorosulfonylimide salt (1) with ethylenecarbonate was used as the starting material and the electrolyte solutionpreparation solvents and the above-mentioned another electrolyte saltwere added to the electrolyte solution material, the liquid temperaturewas kept at a lower temperature even the generation of heat occurred. Asa result, the decomposition of the non-aqueous electrolyte solution wasprevented and a non-aqueous electrolyte solution having good quality wasproduced. In addition, the time required for the preparation of thenon-aqueous electrolyte solution was 50 to 60 minutes, and therefore theproduction efficiency was superior compared with Comparative ExampleB-1.

In Comparative Example B-1, in contrast, LiFSI and LiPF₆ were introducedin divided portions in order to control the temperature so as to preventthe decomposition of the non-aqueous electrolyte solution. As a result,although the increase in temperature was prevented, the time requiredfor the preparation of the non-aqueous electrolyte solution became long(120 minutes), and therefore the production efficiency was poor comparedwith Examples B-1 and B-2.

In Comparative Example B-2, LiFSI and LiPF₆ were introduced in oneportion, not in divided portions, after the preparation of thenon-aqueous solvent solution. As a result, although the time requiredfor the preparation of the non-aqueous electrolyte solution was reduced,the increase in temperature was not prevented, and therefore thenon-aqueous electrolyte solution was decomposed and was discolored.

From the results mentioned above, it is found that, when the electrolytesolution material according to the present invention, which contains afluorosulfonylimide salt (1) and a cyclic carbonate-based solvent or acyclic ester-based solvent as the main components, is used, the increasein temperature during the production process can be controlled properly,and therefore an effect of preventing the decomposition of the resultantnon-aqueous electrolyte solution can be achieved and it becomes possibleto prepare a non-aqueous electrolyte solution within a shorter time withhigher efficiency compared with the conventional techniques.

INDUSTRIAL APPLICABILITY

The electrolyte solution material produced by the production methodaccording to the present invention can be used suitably as a materialfor an ionic conductor that constitutes a primary battery, a batteryhaving a charge/discharge mechanism such as a lithium ion secondarybattery and a fuel cell or an electrical storage device (anelectrochemical device) such as an electrolytic capacitor, an electricdouble-layer capacitor, a solar cell and an electrochromic displayelement.

The invention claimed is:
 1. An electrolyte solution material comprisinga fluorosulfonyl imide salt represented by the following general formula(1):

wherein R₁ represents a fluorine atom or fluorinated alkyl group having1 to 6 carbon atoms, R₂ represents an alkali metal ion, and anelectrolyte solution solvent, wherein: a concentration of thefluorosulfonyl imide salt contained in the electrolyte solution materialis at least about 33 mass %, the electrolyte solution solvent is atleast one selected from the group consisting of a dimethyl carbonate, anethylmethyl carbonate and a diethyl carbonate, and a residual amount ofa fluorosulfonyl imide salt production solvent contained in theelectrolyte solution material is 150 ppm or less, the fluorosulfonylimide salt production solvent is at least one selected from the groupconsisting of water, an alcohol-based solvent, a carboxylic acid-basedsolvent, a ketone, a nitrile-based solvent, an ester-based solvent, analiphatic ether-based solvent, a halogen-based solvent, anitro-group-containing solvent, a nitrogenated organic solvent, aglyme-based solvent, and an aromatic hydrocarbon-based solvent, theelectrolyte solution material has a liquid form, and the residual amountof the fluorosulfonyl imide salt production solvent is a total amount inthe electrolyte solution material.
 2. A non-aqueous electrolyte solutionproduced from the electrolyte solution material according to claim
 1. 3.An electrical storage device comprising the non-aqueous electrolytesolution according to claim
 2. 4. The electrolyte solution material ofclaim 1, wherein the residual amount of a fluorosulfonyl imide saltproduction solvent contained in the electrolyte solution material is 100ppm or less.
 5. The electrolyte solution material of claim 1, whereinthe fluorosulfonyl imide salt production solvent is water and at leastone selected from the group consisting of the alcohol-based solvent, thecarboxylic acid-based solvent, the ketone, the nitrile-based solvent,the ester-based solvent, the aliphatic ether-based solvent, thehalogen-based solvent, the nitro-group-containing solvent, thenitrogenated organic solvent, the glyme-based solvent, and an aromatichydrocarbon-based solvent.